Ganging Outboards - Does it work?

Discussion in 'Propulsion' started by CatBuilder, Jan 14, 2012.

  1. DCockey
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    DCockey Senior Member

    Cars don't need 200 HP for acceleration and certainly not for going up hills. They need 200 HP so they get good reviews and meet the expectations of some customers for acceleration, particularly acceleration at part throttle.

    The average mid-size sedan today is quicker 0 to 60 mph (or 0 to 100 kph) than a Corvette was 30 years ago. Changing expectations.
     
  2. WestVanHan
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    WestVanHan Not a Senior Member

    Yes I know all that,but have you tried merging onto the Los Angeles freeways outside of congested areas?
    I assume it's similar elsewhere.

    And I was being generous!! Many have 300 hp nowadays.
     
  3. DCockey
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    DCockey Senior Member

    Not LA but elsewhere. Lower power and slower acceleration requires modification of driving style. I drive differently towing a heavy boat on a trailer. On the other hand I suspect many drivers never go past about half way in accelerator travel.

    Your earlier point is valid in that the constant speed, level ground power requirements for cars and light trucks are considerably less than needed for acceleration and hill climbing.
     
  4. CatBuilder

    CatBuilder Previous Member

    Thanks for participating, DCockey. Much appreciated.

    This is brainstorming, so yes, just about anything workable is on the table within the SOR and within some practical limitations (such as aerating props on the stern).

    I'll answer in red...

     
  5. CatBuilder

    CatBuilder Previous Member

    (this stuff isn't to DCockey, just in general)

    And, I would point out that level ground is all boats ever experience, since there are no "hills" and there is very little need for acceleration.

    And remember... , that the HP you see on the electric motor isn't peak HP. It's just continuous duty HP. Peak HP is 8 to 10 times that amount show at the electric motor's HP in the case of vehicles. That's where we were getting screwed up in the beginning of the thread.

    On an ICE, peak HP is the only rated HP. There is no exceeding it. There is no continuous duty rating, though we routinely see diesels run at 1800 RPM on generators to allow for continuous duty. What is the HP rating at that level? It's not the "horsepower" we see at peak.

    Two completely different HP ratings.

    A more fair comparison would be to rate the ICE at its continuous duty HP rating, which would be significantly lower than its peak HP. Another consequence of this rating is that the electric motor that is smaller in HP than an ICE will likely have much more available peak HP than the ICE as you can get 8 to 10 times the rated out of it for short periods.

    You also can't get peak HP out of an ICE for long periods, since it's going to kill it. I've never met anyone that runs a Yanmar diesel at peak rated HP (3600+RPM) for more than a few seconds.
     
  6. DCockey
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    DCockey Senior Member

    Revised idea. A stern drive unit mounted to a pod under the bridge deck. Make the lower part of the pad just large enough to mount the stern drive unit to. Depth of pod is such that the bottom of the pod just clears the water at static conditions. Electric motor at the top of the the pod under the bridge deck, or in the bridge deck. Belt drive from the motor to the stern drive input. Motor would be in dry location so an industrial TEFC or pump motor should be satisfactory. Maximum propeller diameter is likely to be smaller than optimum but between the range of stern drive ratios available and belt drive pulleys you should be able to optimize prop speed for the maximum diameter prop which will fit.

    I/O drives are very economical and parts are readily available. There's even an outfit selling aftermarket replacement units. Based on their prices a complete stern drive unit with hydraulic trim/tilt cylinders and hydraulic pump would be around $2000. Your power would be a fraction of what they are designed for so drive component durability shouldn't be a problem. Downside is corrosion can be a problem and the rubber bellows, etc need periodic replacement.

    I don't know what the retractable drive alternatives are to a stern drive without getting into a major custom build and development or if something is commercially available then much higher cost.

    I'm not familar with the stern drive internals but it looks possible to put a spacer between the stern drive lower and upper units so that the propeller would be further into the water and/or the bottom of the pod higher above the water. Some older outboards used such spacers for long and extra-long shaft lengths. A spacer could be made as an aluminum weldment and an extended drive shaft would also be needed. But with electric drive you wouldn't need to be concerned about engine exhaust, and presumably not cooling water. The spacer weldments and longer shaft would probably cost considerably more than the I/O but still less than other alternatives.

    This idea may be worth what it cost you.
     
  7. CatBuilder

    CatBuilder Previous Member

    I appreciate any idea here, David. Thank you.

    I will consider it. Sometimes something that may not seem to work will spark a second idea that will work... or with some revision may work well.

    Let me go and find the weight of all of those components to see how we do....
     
  8. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Not really except for a very brief time, and then only if sufficient electric power is available. No electric motor will produce 8 to 10 times it's continuous power except for an very short time, then it will fail.

    Continuous duty power rating is frequently provided for larger industrial and marine IC engines.

    Also should be noted that an IC engine can be run "continously" at it's peak power provided there is sufficient capacity in the radiator and other parts of the cooling system but durability may significantly reduced.

    I don't know if the power ratings advertised for the motors in electric vehicles are the same as used for industrial motors or similar to the SAE and ISO proceedures used for vehicle IC engines. I suspect the latter.

    And trying to exceed the continous rating of an electric motor for very long will fry something, either the motor windings or the supply circut, or if fitted thermal protection will kick in and shut the motor down.
     
  9. waikikin
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    waikikin Senior Member

    Seein' as your keen for ideas, here's one from distant memory(20 + years), dunno if it would work/compromise lubrication/compromise thrust bearings etc etc was maybe complete BS whatever, but I heard about/spoke to 8th hand about a New Zealander that was building a low cost, light weight "Z" drive from out boards that used a lower gear case to turn the drive thru 90 degrees where the power head usually is, 25hp units spring to mind. May be something like this could be useful for your requirements, some one with outboard/engineering Knowledge may know if that right angle drive would be able to do that & allow a more protected diesel or electric drive with a leg that was retractable, I imagine that engineering challenges might exist in connective to the "motor".
     
  10. CatBuilder

    CatBuilder Previous Member

    One more electric motor side note:

    If anyone things electric motors can't accelerate a car, better take a look at this link:

    0-60 in 2.5 seconds...

    http://gas2.org/2009/03/29/worlds-top-10-fastest-electric-cars/


    The YouTube video here shows an electric car smoking a Porsche and a Ferrari.

    http://www.youtube.com/watch?v=BqqtJpfZElQ

    And here's another video of one kicking a Lamborghini's *ss.

    http://www.youtube.com/watch?v=Zof7wTxbBsM

    I'm sure they could provide their rated continuous power, plus a few minutes of peak power in a boat, IMO, if they can do this a street. All they need is a power source.
     
  11. Richard Woods
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    Richard Woods Woods Designs

  12. WestVanHan
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    WestVanHan Not a Senior Member

    That's great.

    But a gas one is quicker and you can drive around all day,or across the country for that matter.
     
  13. CatBuilder

    CatBuilder Previous Member

    No, it's not. The gas ones were all SLOWER and got their *sses handed to them by the electric. Did you watch the same YouTube videos I did??:confused:

    The point of the posts is that there is no difference. Power is power. Torque is torque. An electric motor works just as well as any other type of motor, as evidenced by the thorough *ss kicking of Porsches, Ferraris and Lamborghinis in those videos. And that wasn't even a small *ss kicking. Did you see how far ahead the electric was? No contest.

    What that proves is electric motors are just fine for power.

    As I said in my last post... you just need a power source. Lucky for me, I have a HUGE diesel generator sitting idle and ready to power electric motors, giving them the same range as any other engines.


    I guess my overall point here is that electric motors, unless too heavy (which is very likely so far), are not to be discounted in this thread. They are just as much in the running as any other idea.

    ***Also, a side note:

    **Has anyone seen a GAHP residential heat pump for sale I can buy?? This could change the entire dynamic if I could find one. They are gas absorbtion heat pumps that run from a flame. If I could get my hands on one of those, there would be no generator and therefore, no electric motors.

    Scope creep, I guess...
     
  14. tunnels

    tunnels Previous Member

    who knows the answers of fore and against and the effects of

    I think this thread has lost it origanal meaning and got a little side tracked from where it started .
    Some where theres a point where multipul outboards strung across the back of a boat does little apart from drink lots a fuel ,but speed wont go past a certain point ! where as one single outboard or even twins could be much more efficent and practical .
    The distance apart is something to be debated untill some one actually has done some official testing and is able to write there test results on paper of fore and against and reasons why and what the effects are of distance !!! 2 motors , 3 motors , 4 motors and any number after that . :confused::rolleyes::?::idea:
     

  15. WestVanHan
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    WestVanHan Not a Senior Member

    Didn't need to-I've driven them-any Atom with 250 to 260 hp (toyota,Ecotech,etc) will do 60 mph in about 2.8, which is quicker .
    The 500 hp V8 is crazy...


    I have a Robur
     
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